Reef manta beam (Meters. alfredi) sightings and associated hitchhiker kinds (1987–2019)

Spatial type regarding the exposure really frequently noticed hitchhiker varieties that have Meters. alfredi (mature and you can juvenile E. naucrates) was basically examined of the mapping the latest portion of sightings at every web site (grouped because of the site setting) where in actuality the hitchhiker types was introduce (final amount off sightings where hitchhikers have been noticed / final amount out-of sightings from the site) inside ArcGIS 10.7. People sites with a maximum of nine otherwise a lot fewer sightings (213 web sites) was excluded to attenuate the newest prejudice a reduced amount of sightings could have to your investigation.

Temporary adaptation from the visibility of adult and you can teenager Age. naucrates with Yards. alfredi try examined playing with monthly day collection. So it show provided that time to the top number of sightings (2008–2019) to incorporate an appropriate period from which to help you visualise manner (i.elizabeth., seasonality). The new month-to-month final amount of sightings had been fixed to own questionnaire effort because of the calculating the newest imply month-to-month number of manta light noticed each survey (month-to-month complete manta ray sightings / month-to-month final number off studies).

Generalised linear blended patterns.

Logistic generalised linear mixed models (GLMM) using R v4.0.0 were used to investigate relationships between the presence of the most frequently observed hitchhiker species (adult and juvenile E. naucrates, G. speciosus, and Lutjanus bohar) with M. alfredi and four explanatory variables: sex with pregnancy status, maturity status, site function (determined by the predominant behaviour observed at the site ), and seasonality (NE or SW Monsoon). Due to the low number of recorded associations between M. alfredi and most of the hitchhiker species, only those with sufficient data were included in the GLMM analysis. The same model was used for Remora remora (the most frequently observed hitchhiker species with M. birostris), but without site function, and sex was classified only as male or female as pregnancies were only observed during four sightings. Each GLMM was fitted with a logit link function to the binary response of hitchhiker species presence (1) and absence (0) using the ‘lme4′ R package . Each model contained the manta-ID as a random intercept to account for any temporal autocorrelation arising from individual rays being repeatedly observed . To compare the relative goodness-of-fit, GLMM models without random effects (GLM) were tested. To reliably estimate the parameters, categories of variables with levels observed equal to or less than five times were removed. For example, under the category behavioural activity, the level ‘breaching’ was observed on less than five occasions, so was removed from analysis. The most informative explanatory variables were identified by firstly testing GLMM models with all combinations of explanatory variables. The variance inflation factor (VIF) was used to test models for multicollinearity; the maximum VIF was <1.5. Model performance was assessed using corrected Akaike information criterion (AICc) test statistic using the ‘MuMin' R package , and the DHARMa R package was used to check the model residuals were normally distributed. The highest-ranking models (with the lowest AICc value, S1 Table) for each hitchhiker species were then interpreted in terms of odds ratios (ORs) (the likelihood of the presence of the hitchhiker species in comparison with the reference category). Any models with ?AICc <2 were considered in interpretation of the highest-ranking model . The significance of each explanatory variable was determined by the 95% confidence interval (CI) of OR, whereby a narrower CI indicates a more precise estimation while, in comparison, a wider CI which had a greater uncertainty. A CI that crossed one is considered non-significant. Any ORs with p > 0.05 are not reported.


A total of 4901 Meters. alfredi was basically in person recognized [men = 2442 (50%), female = 2459 (50%)] throughout all in all, 72912 sightings, at which 44071 (60%) was in fact of females [adult = 25700 (58%), juvenile = 18371 (42%)] and you will 28841 (40%) were guys [adult = 25968 (90%), subadult = 1443 (5%), teenager = 1430 (5%)]. Most of the sightings happened all over 353 web sites, of which 95 (27%) was indeed tidy up station [sightings = 24034 (33%)], 53 (15%) was touring areas [sightings = 129 (0%)], and you will 205 (58%) feeding section [sightings = 48749 (67%)].

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